1. Field of the Invention
The present invention generally relates to a blade device. More particularly, this invention relates to a blade device of an angledozer or a tiltdozer as an earth-moving machine, such as, a bulldozer.
2. Description of the Relevant Art
An example of a blade device in a conventional earth moving machine (e.g., a bulldozer; see, e.g., Japanese Utility Model Application Laid-Open No. 59-144063) is shown in FIG. 11. Another example of such conventional earth moving machine (see, e.g., Japanese Utility Model Application Laid-Open No. 56-68040) is shown in FIGS. 12 and 13. In such conventional devices, as shown in FIG. 13, a frame 41 is swingably supported at the rear end thereof by a chassis 40 through pins 42, and a boss portion 47 fixed at the leading center of the frame 41 is swingably connected to a blade 44 through a ball and socket joint 43. Brackets 45 fixed on the right and left sides of the frame 41 and the chassis 40 are connected by right and left lifting actuators 46 through pins. The blade 44 is moved up and down by extending and contracting the lifting actuators 46. Furthermore, the brackets 45 of the frame 41 and the blade 44 are connected by two right and left angling actuators 50 through ball and socket joints 48. By extending and contracting these two angling actuators 50 separately, the blade 44 is angled on the ball and socket joint 43 as shown in dash lines in FIG. 12.
In the example shown in FIG. 11, a tilting actuator 52 is provided through a ball and socket joint between a center bracket 51 fixed at the leading center of the frame 41 and the back surface of the blade 44. On the other hand, in the example shown in FIG. 12, a substantially triangular tilting lever 56 is attached through a ball and socket joint between the center bracket 51 and the back surface of the blade 44, and a tilting actuator 52 is attached to a third end of the tilting lever 56 through a ball and socket joint. In both these examples, the blade 44 is tilted by the extension and the contraction of the tilting actuator 52. If the width of the machine body 40 and the width of the blade 44 are respectively taken as B0 and B1, B0 is smaller than B1.
Although an angling angle .beta.1 shown in FIG. 12 is normally set at a maximum angle of approximately 25.degree. in such conventional blade devices, since this value is small, the following problems arise. One of such problems as shown in FIG. 14, is that a substantial amount of earth and sand windrow S from the blade 44 is likely to be produced by the small angling angle. Furthermore, a smooth earth and sand flow T is not produced depending on the soil; and therefore, workability in backfilling of a ditch or the like is reduced.
As to another problem, since a width B of the blade 44 at the maximum angling angle is larger than a width BO of the chassis 40 (as shown in FIG. 15), the machine with the blade 44 attached cannot be loaded onto a truck having a rear deck width B2 which is a little larger than the chassis BO. In such a case, prior to transporting the machine, it will be necessary to detach the blade 44 in order to load the machine onto the truck. After transporting the machine, it will be necessary to again attach the blade 44 to the machine. In accomplishing such cumbersome procedures, additional man-hours will be required.
Accordingly, as shown in FIG. 16, a maximum angling angle .beta.2 is required to be made wider in order to obtain a width B6 of the blade 44, which is smaller than the chassis width BO for the purpose of improving transportability. In this case, it is necessary to increase the stroke of the angling actuators 50 by positioning a pivot center 53 of the blade 44 ahead of the chassis 40. Therefore, when the angling angle is increased in the conventional structure, the distance between the blade 44 and the chassis 40 is increased.
However, as shown in FIG. 17, if the length from the center of a drive tumbler 54 to the front end of the blade 44, the length from the center of the drive tumbler 54 to the center of gravity G of the machine, and the weight of the machine are taken as Lf, Lw and W, respectively, since an edge force F of the blade 44 equals (Lw/Lf)x W, such edge force F decreases as the length Lf increases; thereby, causing a problem due to a decrease in the operation capability of the machine. In addition, since a length L1 of such conventional blade device also increases with the increase of the length Lf, the blade change amount with respect to the amount of control by the operator increases, and therefore, it is difficult to control the blade 44 of the conventional blade device. Furthermore, the stroke of the angling actuators 50 is lengthened, and rods of the angling actuators consequently buckle. In order to prevent such buckling, an increase in the actuator thrust is essential, which however increases the production cost. Also, since the length of the machine is increased, the weight is increased and the production cost thereof is further increased.
Although other conventional blade devices equipped with angling actuators are disclosed in Japanese Utility Model Application Publication Nos. 56-13415 and 56-47251, and Japanese Utility Model Application Laid-Open Nos. 3-65754, 3-65755 and 3-119054, none of these conventional devices teach the increase of the angling angle.